We propose to study the effect of duration of cardiopulmonary bypass on a) endogenous circulating levels of norepinephrine (NE), 5-hydroxytryptamine (5-HT), prostaglandin E2 (PGE2) and prostaglandin F2alpha (PGF2alpha); b) extraction of radiolabelled NE, 5-HT, PGE, and PGF2alpha in pulmonary, renal and hindlimb vasculatures; and, c) peripheral hemodynamics and capillary permeability.